a) Field of the Invention
The present invention relates to an ion implantation system and method, and more particularly to a serial wafer processing type ion implantation system and method suitable for high dose ion implantation of large diameter wafers.
b) Description of the Related Art
Conventional high current ion implantation for wafers has used batch processing. For example, a plurality of wafers are placed on an inner circular cone surface of a circular cone plate in the circumferential direction. As the circular cone plate is rotated around its center axis, wafers revolves around the center axis of the circular cone plate. Each revolving wafer traverses an ion beam radiation area on a revolving orbit and ions are implanted at that time.
Each wafer placed on the inner surface of the circular cone plate is pushed against this surface by the centrifugal force. The inner surface of the circular cone plate is made of rubber or the like having good thermal conductivity so that the wafers in tight contact with the inner surface are cooled. Each wafer is heated once per one revolution while it is exposed to ion beams, and it is cooled during the other period. The temperature is maintained at 90 to 100.degree. C. or lower during ion implantation.
A plurality of wafers are disposed in the circumferential direction in the above-described batch processing system. Therefore, if each wafer is large, the system becomes bulky. Furthermore, since the number of batch-processed wafers is large, if the wafer size is large, a number of chips are processed at the same time. This is not suitable for small production of many product types. Rotation of a circular cone may generate particles which may lower production yield.